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Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes)

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Hi Salvatore,

>> 52fbe173baa4df9d14bd733f42ee6b9ceab8299b is the first bad commit
>> commit 52fbe173baa4df9d14bd733f42ee6b9ceab8299b (HEAD)
>> Author: Ricardo Ribalda <ribalda@chromium.org>
>> Date:   Wed Dec 18 21:39:09 2024 +0000
>>
>>      media: uvcvideo: Invert default value for nodrop module param
>>
>>      The module param `nodrop` defines what to do with frames that contain an
>>      error: drop them or sending them to userspace.
>>
>>      The default in the rest of the media subsystem is to return buffers with
>>      an error to userspace with V4L2_BUF_FLAG_ERROR set in v4l2_buffer.flags.
>>      In UVC we drop buffers with errors by default.
>>
>>      Change the default behaviour of uvcvideo to match the rest of the
>>      drivers and maybe get rid of the module parameter in the future.
>>
>>      Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>>      Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
>>      Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>>      Reviewed-by: Hans de Goede <hdegoede@redhat.com>
>>      Link: https://lore.kernel.org/r/20241218-uvc-deprecate-v2-2-ab814139e983@chromium.org
>>      Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>>      Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
>>
>>   drivers/media/usb/uvc/uvc_driver.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> I added Ricardo in Cc. Ricardo, see
>> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1121718 for context.
>>
>> The bug does not always immediately manifest, so there is a small chance
>> that for some of the commits that I marked "good", artifacts would have
>> started appearing if I had waited a bit longer. But the commit seems
>> reasonably plausible to be able to cause the kind of error I am seeing.
>>
>> Given that this is about a module parameter, I assume I could test this by
>> booting the latest kernel and setting the parameter back to its previous
>> value... but I don't know enough about how the kernel works to actually do
>> that.^^ Happy to try that if someone gives me some pointers.
> 
> You can create a modprobe.d file /etc/modprobe.d/uvcvideo.conf with
> 
> options uvcvideo nodrop=0
> 
> to pass 'nodrop=0' parameter when loading the uvcvideo module (then
> unload and load the module).

Thanks, that seems to have worked! So at least for now this is a viable 
work-around...

> But it already warns in dmesg when doing so with:
> 
> uvcvideo: [Deprecated]: nodrop parameter will be eventually removed.

... but only until the parameter gets removed, of course.

Kind regards,
Ralf

> 
> Regards,
> Salvatore

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Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Salvatore Bonaccorso <carnil@debian.org> - 2025-12-02 17:50 +0100
  Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2025-12-02 18:50 +0100
    Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2025-12-08 19:50 +0100
    Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2025-12-17 14:20 +0100
      Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Salvatore Bonaccorso <carnil@debian.org> - 2025-12-17 20:30 +0100
        Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2025-12-17 20:40 +0100
          Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2025-12-18 14:20 +0100
      Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2026-01-02 14:30 +0100
        Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Salvatore Bonaccorso <carnil@debian.org> - 2026-01-02 15:10 +0100
          Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2026-01-02 17:40 +0100
            Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2026-01-05 16:50 +0100
            Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Laurent Pinchart <laurent.pinchart@ideasonboard.com> - 2026-01-05 19:10 +0100
            Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2026-01-05 20:30 +0100
              Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2026-01-20 15:30 +0100

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